While prince bedtime stories are often associated with children, adults can appreciate the rich cultural and literary history behind them. Many classic stories have been adapted and retold over the years, and adults can enjoy exploring different versions and interpretations. Also, some people might use these stories as a form of relaxation before sleep, just like children do.
Another moral is the value of simplicity. In a world full of complex adults and their strange behaviors, the Little Prince's simple view of things makes us think. He values the stars for their beauty and the simple things in life, which we often overlook in our pursuit of more material things.
Kids might enjoy 'Thumbelina'. In this story, Thumbelina meets a prince who is also a tiny being like her. It's a sweet and magical story. 'The Emperor's New Clothes' also has elements related to a prince - like figure (the emperor). The story teaches kids about honesty as the emperor is fooled by the weavers. And 'Hansel and Gretel' can be thought of in terms of the kids outwitting the witch and then living happily ever after, similar to how a prince might rescue and have a happy ending.
I think one of the main themes is the exploration of innocence. The Little Prince has a pure and innocent view of the universe. He doesn't understand the grown - up world's complexity and materialism at first. His journey is also a journey of maintaining that innocence while learning about different aspects of life through his encounters. For example, when he meets the businessman who is only concerned with counting the stars he owns, the Little Prince is puzzled because his idea of the stars is more about beauty and wonder rather than ownership.
Some fanfics focus on their military service as well. Given that both princes have served in the military, stories might be written about their experiences during their service, how it has shaped them, and how it affects their relationship as brothers. Additionally, there could be themes related to their charity work, with fanfics depicting them working together on various charitable initiatives and the impact they have on the communities they serve.
Maybe the prince is from a neighboring magical country. For example, he could be from a place like Beauxbatons or Durmstrang. He comes to Hogwarts on an exchange program of sorts and that's where he meets Harry and decides to court him. This would add an element of international magical relations to the fanfic.
There are many fanfics that might explore their relationship as brothers. Some could be about their growing up years together at the palace, like imagining their adventures in the palace gardens or during family holidays. Another type could be set in a fictional future where they work together on a major royal project for the betterment of the country.
It could be an original character created just for this fanfiction. Maybe a prince from a hidden magical realm that has been kept secret from the wizarding world until now.